Electrode coated with a film obtained from an aqueous solution comprising a water-soluble binder, production method thereof and uses of same

ABSTRACT

A method of preparing an electrochemical electrode which is partially or totally covered with a film that is obtained by spreading an aqueous solution comprising a water-soluble binder over the electrode and subsequently drying same. The production cost of the electrodes thus obtained is reduced and the surface porosity thereof is associated with desirable resistance values.

CROSS REFERENCE TO RELATED APPLICATIONS

The present application is a divisional of U.S. application Ser. No.15/455,266, filed on Mar. 10, 2017, which is a continuation of U.S.application Ser. No. 15/014,469, filed on Feb. 3, 2016, now U.S. Pat.No. 9,692,040, which is a continuation of U.S. application Ser. No.10/534,697, filed on Nov. 16, 2005, now U.S. Pat. No. 9,293,769, whichis a U.S. national stage of International Application No.PCT/CA2003/001739, filed on Nov. 13, 2003, which claims the benefit ofCanadian Application No. 2,411,695, filed on Nov. 13, 2002. The entirecontents of each of U.S. application Ser. No. 15/455,266, U.S.application Ser. No. 15/014,469, U.S. application Ser. No. 10/534,697,International Application No. PCT/CA2003/001739, and CanadianApplication No. 2,411,695 are hereby incorporated herein by reference intheir entirety.

TECHNICAL FIELD

The present invention relates to a new process for preparingelectrochemical electrodes and electrodes thus obtained. The processmakes it possible to prepare electrodes that are completely or partlycoated with a film obtained by spreading and drying, on the electrode,an aqueous solution containing a water soluble binder and an activematerial.

A second aspect of the invention concerns processes for preparingelectrochemical systems involving at least one step for preparingelectrodes according to the invention and the electrochemical systemsthus obtained.

A second aspect of the present invention relates to the use of a watersoluble polymer, as a binder in an aqueous solution for the preparationof a film for coating part or the totality of an electrode.

The present invention also provides a new process for manufacturing aLi-ion natural graphite/electrolyte/LiFePO₄ battery, which is allliquid, all gel or solid.

PRIOR ART

U.S. Pat. No. 6,680,882 describes an aprotic electrolytic compositionthat is placed in a separator and in at least one composite electrodecontaining a powder of an active material. The electrolytic compositionused comprises a first polymer matrix consisting of a polymer and atleast one second polymer matrix as well as at least one alkali salt anda polar aprotic solvent. This process has the disadvantages associatedwith the use of binders of the PVDF type as diluted in solventsclassified as toxic with respect to the environment.

SUMMARY

The invention relates to a process for preparing an electrode that is atleast partly coated with a film obtained by spreading and drying, on anelectrode support, an aqueous solution comprising at least one activematerial, at least one water soluble binder and at least one watersoluble thickener. Besides its economic advantages, the processovercomes the environmental problem involved when using organicsolvents. The electrodes thus obtained are performing and canadvantageously be used in the manufacture of electrochemical systemsthat are stable and highly performing.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a schematic representation of a process according to anembodiment of the invention for the preparation of lithium ion batteriesby extrusion.

FIG. 2 represents an elliptic cross-section of the elements of a lithiumion battery according to the invention.

FIG. 3 is a schematic representation of a bi-cell structure for polymercells.

FIG. 4 is a schematic representation of a metal plastic wrapping withoutHF protection layer for non-polymer batteries.

FIG. 5 represents the charge-discharge curve of a graphite/Celgard(EC-DMC-LiBF₄)Li anode prepared with a water soluble binder.

FIG. 6 represents the charge-discharge curve of a LiFePO₄/Celgard(EC-PC-DMC-LiBF₄)Li cathode prepared with a water soluble binder.

DETAILED DESCRIPTION

Within the framework of the present invention the term binder means anychemical compound whose function is to connect the active particlestogether in order to provide a chemical or electrochemical network thatis favorable to conduction.

Within the framework of the present invention the term thickener meansany chemical compound that is capable of increasing the viscosity andthe wettability of the hydrophobic particles that are present in theconcerned solutions.

A first object of the present invention consists of a process forpreparing an electrode that is at least partly coated with a filmobtained by spreading and drying, on an electrode support, an aqueoussolution comprising at least one active material, i.e. chemically and/orelectrochemically active, at least one water soluble binder and at leaston water soluble thickener.

Spreading is advantageously carried out by traditional techniquesdescribed for example in Coating Technology Handbook by Satas Armek1991, part II, Coating and Processing Technics pages 103 to 321. Dryingof the film that is spread on the electrode is advantageously carriedout for a period between 1 and 2 hours and at a temperature preferablybetween 80 and 130° Celsius.

The active material used is advantageously selected from the groupconsisting of:

-   -   metallic oxides;    -   ceramics;    -   carbon, natural graphite and synthetic graphite;    -   metals;    -   semi-conductor materials; and    -   mixtures of at least two thereof.

According to another advantageous embodiment, the metallic oxide isselected from the group consisting of LiMn₂O₄, LiCO₂ and LiNi₂. For itspart, the carbon may be selected from the group of high surface carbon,graphite, carbon fibers and cokes. The metals that are advantageouslyretained are selected from the group consisting of Ag, Sn and Cu. Amongthe semi-conductor materials, silicon gives particularly interestingresults.

The chemically and/or electrochemically active material used isgenerally in the form of powder whose average particle size is between10 nanometers and 10 millimeters and having a relatively low granulardispersion advantageously corresponding to a gap of D50−D10=30 and a gapof D90−D50=30.

According to a preferred mode, for example for the preparation ofelectrodes for automobile batteries, the powder that is retained has agranular dispersion between 200 nanometers and 25 micrometers.

At least 20% of the binder and thickener retained are generally watersoluble when they are introduced, at room temperature, at the rate of 20grams in 200 grams of water. Preferably, at least 50% and still moreadvantageously at least 90% are soluble.

The water soluble thickener may be selected from the group consisting ofnatural celluloses, physically and/or chemically modified celluloses,natural polysaccharides, chemically and/or physically modifiedpolysaccharides and which have a molecular weight between 27,000 and250,000.

The thickener is advantageously selected from the group consisting ofcarboxymethylcelluloses,hydroxymethylcellulosesandmethylethylhydroxycelluloses.

According to a preferred mode, the thickener is selected from the groupconsisting of carboxymethylcelluloses, of the Cellogen® type sold byDai-ichi Kogyo Seiyaku Co. of Japan for example under the commercialdesignations EP, 7A, WSC, BS-H and 3H.

The soluble binder is advantageously selected from the group consistingof natural and/or synthetic rubbers.

The binder is of the non-fluorinated type or of the low fluorinatedtype. Indeed, by way of example, LiF, not being soluble in water, cannotbe used in the context of the invention.

Among the rubbers, those of the synthetic type and more particularlythose selected from the group consisting of SBR, (styrene butadienerubber), NBR (butadiene-acrylonitrile rubber), HNBR (hydrogenated NBR),CHR (epichlorhydrin rubber) and ACM (acrylate rubber) are particularlyadvantageous.

The soluble rubbers used, and for example those of the SBR family, arepreferably in the form of a paste.

By way of example, SBR sold by NIPPON ZEON'S BINDER BATTERY GRADE undercommercial designation (BM-400B) or equivalent and the thickeners of theCellogen® known under the abbreviations EP and/or 3H may be mentioned.

Normally, the thickener/binder ratio varies between 10 and 70%,preferably between 30 and 50%.

The binder content is advantageously between 1 and 70%, and that of thethickener is between 1 and 10%, in the aqueous solution.

An aqueous solution that is adequately used for spreading on an anodesupport may be formulated as follows, the percentages being given inweight:

-   -   at least 64% graphite; and    -   at least 3% water soluble binder,    -   from 0.1 to 2% thickener; and    -   at most 27% water.

An aqueous solution adapted for spreading on a cathode support may beformulated as follows, the aqueous solution used for spreadingcontaining by weight:

-   -   at least 64% LiFePO₄; and    -   at least 3% water soluble binder,    -   from 0.1 to 2% thickener; and    -   at most 27% water.

When implementing the process, the electrode is dried by removing,preferably, at least 95% of water that is present in the solution usedto carry out the spreading step.

Various techniques known to one skilled in the art can be used to removethe traces of H₂O that are present at the surface of the electrode,after coating the latter with the aqueous solution. These traces ofwater are removed by thermal means on line of the EXT, DBH and/or DBprocess, or by infra-red at a temperature advantageously between 80 and130° Celsius for a period between 1 and 12 hours.

The film is advantageously dried until its residual water content islower than 2000 ppm and preferably lower than 50 ppm.

This process is advantageously applied to electrodes of the non-saltedtype, i.e. to the electrodes of the invention made of an activematerial, carbon and a thickener and/or a binder.

The process is usually carried out at room temperature and pressure. Aninert atmosphere may be used, as well as a partial vacuum during thedrying step. Because no organic solvents are used, the extrusion processis particularly important. Indeed, the risks inherent to the use ofsolvent, such as risks of explosion are set aside and the work can becarried out, for example according to an embodiment, by extrusion, undermore energetic conditions, for example at extrusion speeds that can beas much as 20% higher.

For the production of negative electrodes according to the invention,the electrochemically active material used may be selected from thegroup consisting of graphite, Sn alloys, Si alloys, LiT₅O₁₂, WO₂ typepowders and mixtures obtained from at least two of these powders. By wayof examples of such powders, those consisting of particles having anellipsoidal graphite nucleus coated with prismatic shaped graphiteparticles, may be mentioned. Coating of ellipsoidal graphite withprismatic graphite may be obtained by mechano-fusion, also known asmechano-melting and/or hybridization.

When it is desired to prepare a positive electrode, theelectrochemically active material is preferably selected from LiCoO₂,LiNiO₂, Li₂Mn₂O₄, LiNi_(0.5)Mn_(0.5)O₂, LiFePO₄ powders that are coatedwith graphite and carbon and mixtures of at least two thereof.

For example, electrodes of the type LiFePO₄ coated with graphite and/orcarbon can be obtained. Coating LiFePO₄ with graphite and/or carbon isnormally carried out by mechano-fusion, also known as mechano-meltingand/or by hybridization.

The specific surface area of the carbon that is present in the coatingmay vary widely; the one measured by BET, was identified as being inmost cases higher than or equal to 50 m²/g.

This process also makes it possible to prepare an electrochemicalseparator that is at least partly coated with a film of the polymertype, preferably of the water soluble SBR type.

Such a process for preparing an electrochemical separator is inaccordance with the processes of preparing electrodes as previouslydefined, except that the aqueous polymer solution used contains noactive materials nor carbon or only very small quantities thereof.Indeed, the separator is used for ionic transport between the anode andthe cathode, and it is not electronically conductive.

A second object of the present invention consists of an electrode thatis made of a support that is coated at least in part with a filmcontaining an active material, the electrode being obtained byimplementation of one of the processes according to the first objectpreviously defined. These electrodes are characterized in that thebinder, after drying the aqueous solution used to constitute thespreading film, is pulled away from the support.

In the case of a cathode, the electrode support advantageously comprisesat least in part stainless, aluminum, copper, carbon, metal-plastic or amixture of at least two of these materials.

In the case of an anode, the electrode support advantageously comprisesat least in part copper, metal-plastic, or a mixture thereof.

The electrodes of the invention have advantageously at least one of thefollowing properties:

-   -   storage stability, preferably greater than 1 year, in the        presence of a moisture content higher than 50% and in the        presence of temperatures higher than 20° Celsius;    -   a film thickness, when the latter is graphite based, that is        between 10 and 100 μm, still more preferably between 20 and 45        μm and according to the most advantageous mode the film has a        thickness of about 45 μm;    -   a film thickness when the latter is iron and/or phosphate based,        that is between 20 and 200 μm, still more preferably between 20        and 110 μm, the most advantageous mode being the one in which        the film has a thickness of about 90 μm;    -   electrochemical performances that compare to those of        corresponding electrodes obtained with the same active material        but by using an organic solvent solution;    -   an electrode film characterized by the fact that particles of        rubber are directly attached to the electrode support; and    -   a porosity of the film that coats one or more of the electrodes,        measured by the method of measuring thicknesses, that is between        10 and 90%, preferably between 30 and 40%.

A third object consists of a process for preparing an electrochemicalsystem by assembling is constituents including at least one anode, atleast one cathode and at least one separator, in which at least oneanode and/or at least one cathode has been obtained by a processaccording to the first object of the invention or as defined in thesecond object of the invention.

This process is advantageously used for the preparation of a battery inwhich the separator is porous. The separator is for example of thepolypropylene or polyethylene type or of the (PP,PE) mixture type andobtained by extrusion, and/or of gel type.

The separator is preferably obtained from polymer materials of the type:

-   -   polyester,    -   poly(vinylydienefluoride), also called (PVDF), of chemical        formula (CH—CF₂)_(n), in which n preferably varies between 1000        and 4000, preferably such that n is close to 150; among those        polymers those having an average molecular weight between 10,000        and 1 million, still more preferably those having an average        molecular weight between 100,000 and 250,000 are particularly        interesting;    -   poly(vinylydiene fluoro-co-hexafluoropropene) copolymers, of        formula [(CH₂—CF₂)_(x)(CF₂—CF(CF₃))_(1-x)]_(n) also called        (PVDF-HFP), in which n varies between 1000 and 4000, preferably        n varies from 2000 to 3000, still more preferably n is close to        150 and x preferably varies between 0.12 and 0.5; among those        polymers, those having an average molecular weight between        10,000 and 1 million, still more preferably those having an        average molecular weight between 100,000 and 250,000 are        particularly interesting;    -   poly(tetrafluoroethylenes), also called (PTFE), of chemical        formula (CF—CF₂)_(n), in which n varies between 5 and 20,000,        preferably n varying from 50 to 10,000; among those polymers,        those having an average molecular weight between 500 and 5        million, still more preferably those having an average molecular        weight between 5,000 and 1,000,000, preferably about 200,000 are        particularly interesting;    -   poly(ethylene-co-propylene-co-5-methylene-2-norbornenes) or        ethylene propylene-diene copolymers, also called EPDM,        preferably those having an average molecular weight between        10,000 and 250,000, preferably between 20,000 and 100,000; and    -   poly(methylmethacrylates) also called (PMMA), of formula        [(CH₂—C(CH₃)/(CO₂CH₃)]_(n), in which n preferably varies between        100 and 10,000, still more preferably n varying from 500 to        5000; among those polymers, those having an average molecular        weight between 10,000 and 1 million, preferably those having an        average molecular weight between 50,000 and 500,000, are        particularly interesting; and    -   mixtures of at least two of these materials.

The preparation of this type of separator is advantageously carried outby utilizing the techniques described in Coating Technology Handbook bySatas Armek 1991, part II, pages 103 to 321, Coating and ProcessingTechniques.

By way of examples of known separators one may mentioned those of thePEO-PPO polyether copolymer type, those of the 3 branch polyether typeas defined for example in U.S. Pat. No. 6,190,804 or those of the 4branch polymer type as defined in U.S. Pat. No. 6,280,882. The contentof these two patents and, in particular respectively columns 1 and 2, isincorporated by reference in the present application.

Particularly interesting results have been obtained by using a separatorobtained from the 4 branch polyether manufactured by DKS Japan and soldunder the trademark ELEXCEL® ERM1.

A fourth object of the present invention consists of electrochemicalsystems capable of being obtained by a process according to the thirdobject of the present invention, as well as those comprising at leastone electrode obtained by implementation of a process according to thefirst object of the present invention.

In systems of this nature one of the originalities resides in the factthat the polymer solution has dried at the surface of the electrodesupport and that the result, for example in the case of aqueoussolutions of SBR, is a binding of SBR at the surface of the electrodesupport.

In systems of this nature, the separator may be of the gel, solid orliquid electrolyte type and it is advantageously of the gel type.

According to an advantageous embodiment, the electrolyte includes aleast one salt and at least one solvent.

The molar concentration of salt in the electrolyte, is then preferablylower than or equal to 1, and the molar concentration of solvent, forits part, is advantageously higher than or equal to 1.

The salt that is used is preferably a salt of the imide family, of thetype LiPF₆, LiBF₄, LiBOB, LiTFSI or LiFSI or mixtures thereof, such as amixture of LiBOB and LiFSI.

The solvents used preferably have a high boiling point that is higherthan 100° Celsius. Such solvents may include those of the type γ BL,TESA, or modified TESA, or mixtures of at least two of these solvents.

EC (ethylene carbonate) and PC (propylene carbonate) solvents arenormally used for the formation of a passivation film in the case ofcarbon based anodes, and the PC solvent is used to achieve lowtemperature applications.

In such systems, the electrolyte for the all gel battery isadvantageously obtained from a precursor of a compound of a) apolymer+b) a liquid electrolyte.

The content of a) may vary between 1 and 99%, preferably this contentvaries between 5 and 25%; and the content of b) may vary between 1 and99%, preferably this content varies between 75 and 95% and the contentsa and b agree with the relation (a)+(b)=100%, the % being given byweight.

According to another advantageous embodiment, the thermo-initiator isadded in quantities that are in proportion to the total weight a)+b),i.e. preferably in amounts between 100 and 5000 ppm, still morepreferably between 500 and 1000 ppm.

The composition of the polymer is preferably low i.e. about 5% of a 4branch polyether, preferably of the ELECEL® type and about 95% of anelectrolyte of composition (1.5 LiTFSI+EC+PC+TESA+γBL (1:1:1:1)).

For its part, the lithium salt concentration is advantageously higherthan or equal to 1 M (1 molar) in the case of gels, and the lithium saltconcentration is lower than or equal to 1 M (1 molar) in the liquidelectrolyte.

Among these electrochemical systems, one may advantageously mentionthose including at least one anode, at least one cathode and at leastone separator and in which at least two, and preferably at least threeof the constituents of the system have been prepared by implementationof any one of the processes according to the first object of theinvention.

Similarly, the electrochemical systems in which the constituents havebeen substantially prepared without using organic solvents, areparticularly interesting, and those obtained without any organic solventare preferred.

A fifth object of the present invention relates to the use of a watersoluble polymer, preferably a polymer of the styrene butadiene rubbertype, still more preferably a SBR sold by NIPPON ZEON'S BINDER BATTERYGRADE (BM-400B) as a binder in an aqueous solution for the preparationof a film for coating part or the totality of an electrode support.

This use has the advantage of being used, without any formation of HF,due to the fact for example of the use of an imide salt in place ofLiPF₆ which is found in commercial batteries.

Preparation of the film is carried out by cross-linking the polymersolution that coats the electrode for example by thermal radiation afterthe electrode has been placed in the battery and the battery has beensealed.

The polymer solution is normally selected so that the polymerizationtemperature is between 40 and 80° Celsius and so that cross-linking ofthe polymer solution is carried out by infra-red.

The time of cross-linking of the polymer is advantageously between 5minutes and 2 hours.

By way of example, polymerization is carried out at about 80° Celsiusand during about 10 minutes.

The use of the invention is particularly adapted for the manufacture ofbatteries of the flexible type such as those of the multi-layer metalplastic type.

This use allows a reduction of the manufacturing costs for example dueto the fact that it is no more required to have a protective layeragainst HF and also due to the fact that the costs concerning organicsolvents are eliminated.

Another particularly interesting application resides in the preparationof super condensers preferably in the preparation of super condensers ofthe hybrid type as well as in the preparation of cathodes from analuminum type of support of the expanded metal EXMET® type.

Another interesting variant resides in the use of an anode support ofthe copper type, preferably EXMET, for the preparation of anodes, whenthe average voltage is lower than or equal to 1.6 Volts and the cathodesupport is made of aluminum when the average voltage is higher than 1.6Volts.

DESCRIPTION OF PREFERRED EMBODIMENTS

Generally, during implementation of the processes of the invention, theso called high speed techniques such as extrusion or vertical spreadingon EXMET may be used, however extrusion is the recommended process.

The binder without fluorine is dissolved in water which facilitates theprocess of extrusion and increases the speed of the processes.

The presence of graphite in the anode and in the cathode acts aslubricant and makes it possible, for example, when utilizing extrusion,to homogenize the thickness of the electrode and to decrease itsresistance by controlling porosity.

The solvent used, whether dealing with the anode or the cathode, iswater, which makes the process safe, environmentally safe and notexpensive. The use of an imide type of salt (without formation of HF)provides for a good conductivity of the electrolyte and increases thesecurity of the battery.

The new process according to the invention is applicable for example tothe production of inexpensive and safe Li-ion batteries. Such batteriesinclude at least the 4 following parts: an anode; a cathode; aseparator; an electrolyte.

EXAMPLES

The following examples are given purely as illustration and should notbe interpreted as constituting any kind of limitation of the invention.

1. Use of the Process for the Preparation of an Anode

The anode is made of spherical graphite particles having an average sizeof 20 μm, that are coated with 1% of particles of a prismatic graphitewhose size is 4 μm; mixture is ensured by mechano-fusion, also known asmechano-melting or by hybridization. In this manner, 95% of graphite ismixed with 5% of a SBR such as (NIPPON ZEON'S BINDER BATTERY GRADE(BM-400B)) that is used as binder, the latter being put into solution inwater.

An optimum concentration is selected for the extrusion or spreading oncopper (preferably on an expanded metal called EXMET).

The spherical graphite is selected because of the lithium diffusionspeed at its surface and of its reversible capacity of the order of 370mAh/g. For its part, prismatic carbon is selected as a conductivitybridge between the spherical particles, which decreases the resistanceof the electrode. The purpose of using prismatic graphite (associatedwith the presence of basal surfaces) is to make sure that the electrodeis lubricated; in particular during extrusion or spreading, which hasthe effect of homogenizing the thickness and the porosity of theelectrode. On line drying by infra-red simplifies the machinery and theprocess.

Heating is also used to remove traces of water (H₂O). The fact that theelectrode is not salted (no salt) permits to improve the electrochemicalperformances of the battery without production of HF.

The other advantage associated with this electrode is the use of anon-fluorinated binder, which eliminates all reaction with theelectrolyte or all parasite reaction with formation of HF. This has aninfluence on the choice of the multilayer material, of the metal plasticthat is used as battery casing and makes it possible to prevent using aprotective layer against HF, which limits by as much manufacturingcosts.

In this process, the starting solvent is water. This is beneficial tothe environment and requires no special installation (such as ananhydrous chamber for the recovery of the solvent with specialprecautionary measures).

2. Use of the Process for the Preparation of the Cathode

The cathode preferably consists of LiFePO₄ (from Phostech Inc.). LiFePO₄is coated with 3% Ketjen black and 3% natural or artificial graphite.The coating process is made possible by mechano-fusion, also known asmechano-melting or by hybridization.

Ketjen black is used to constitute the electronic conductivity networkin the electrode. Graphite has a double function. First, it provides ajunction bridge between LiFePO₄ and Ketjen black, which brings a lowresistance to the electrode. Graphite also acts as lubricant tofacilitate spreading, in particular by extrusion, by providing anelectrode with a good uniformity and a controlled porosity.

The compound LiFePO₄/carbon (Ketjen black)/graphite is mixed with 5% SBRbinder, from (NIPPON ZEON'S BINDER BATTERY GRADE (BM-400b)) that is putin solution by dissolution in water.

Spreading of the composite is carried out by extrusion or by DoctorBlade (horizontal or vertical), preferably by extrusion. Drying isachieved as in the case for the preparation of the anode described inpart 1, that uses infra-red.

The process that is used for the preparation of the cathode is similarto the one used for preparing the anode.

It requires the use:

-   -   of H₂O as solvent;    -   of a lubricating and conductive graphite;    -   of infra-red as drying means; and    -   of a binder without fluorine of the type SBR; (NIPPON ZEON'S        BINDER BATTERY GRADE (BM-400B).

It permits to prevent using:

-   -   a salt;    -   an anhydrous chamber; and    -   special precautionary measures.

LiFeO₄ is completely charged at 3.8 Volts, without for this reasondecomposing the SBR of (NIPPON ZEON'S BINDER GRADE(BM-400B). The use ofan imide type of salt has no effect on the corrosion of the aluminumcollectors, preferably of the type EXMET, which is advantageous for theenergy density of the battery.

3. Process for Preparing a Separator

a. Separator for Liquid and Electrolyte Gel

-   -   The separator is preferably of the PP (polypropylene) or PE        (polyethylene) type or mixtures thereof. It is preferably        obtained by extrusion. The porosity of this separator is about        30 to 50%, which gives more space for the electrolyte and in        particular for the gel. This membrane is called “Free Solvent”.        The separator is cross-linked by UV thermal heating, E-Beam, or        IR (thermal). Cross-linking is preferably carried out by IR on a        protection line.

b. Polymer Separator

-   -   The use of this separator in the battery still limits the use of        PP or PE. The advantage of a separator made of a polymer is for        security reason, since it forms a physical and chemical gel with        the electrolyte.    -   The separator is preferably made of a polyether of the PEO-PPO        copolymer type (polyoxyethylene-polyoxypropylene) of the 3        branch or 4 branch type, preferably a 4 branch polyether (sold        by DKS under the designation Elexel® 217). These polyethers are        practically liquid at room temperature. Their use within the        framework of the extrusion process requires no addition of        solvent, which overcomes the problem of harms to the        environment.    -   Cross-linking of this type of polymer is carried out thermally        by E-Beam, IR or UV.        4. Assembling a Li-Ion Battery (FIGS. 1-4 )

a. All Liquid

-   -   The three films anode/separator: PP or PE/cathode are wound        together according to the desired capacity (in mAh or Ah); when        winding, a pressure of 10 psi is applied. Tabs (current        connectors) of the Al and nickel type are welded by ultrasound        (ATM207), respectively on the Al collector of the cathode and        the copper of the anode.    -   The 3 film winding is introduced into a metal plastic bag,        without HF protector.    -   Injection of the liquid electrolyte is carried out after        achieving a complete vacuum in the metal plastic bag. The liquid        electrolyte is a mixture of salts and solvents, the salt is of        the imide type such as LiTFSI and/or LiFSI, the solvent or the        mixture of solvents used preferably has a high boiling point. By        way of example of solvents that can be used in this context, the        following mixtures are mentioned:        -   EC+γBL        -   EC+TESA (or modified TESA)        -   or        -   PC+EC+γBL        -   PC+EC+TESA (or modified TESA)        -   PC+EC+γ BL+TESA (or modified TESA)    -   Concentration of the salt in the case of liquids is ≤1 M (1        molar). Once the battery has been sealed, the electrochemical        formation of the battery is carried out by applying small        currents to obtain a uniform passivation film on the surface of        the anode (graphite/ellipsoid).

b. Gel with PP or PE Separator

-   -   The process of part 4b is essentially the same as the one        described in part 4a.    -   The electrolyte gel precursor is made of 5% polymer (Excel)+95%        (1.5 M LiTFSI)+EC+PC+γ BL 1:1:3)+1000 ppm of a thermo-initiator        that is preferably Perkadox 16. This combination does not limit        the choice of the electrolyte.    -   The electrolyte is injected after achieving a complete vacuum in        the bag of the battery, including the 3 films (anode/separator        PP/cathode).    -   Once the battery has been sealed, the gel is obtained by thermal        treatment at 80° Celsius, during 10 minutes, preferably by IR        during 10 minutes. An in situ impedance measurement follows the        evolution of the resistance of the electrolyte. After        implementation of the polymerization, the battery is        electrochemically formed, as in the equivalent portion of part        4b. The gel concentration is then constant in the separator, in        the anode and in the cathode.

c. Gel with Polyether Separator

-   -   The 3 films anode/polyether/cathode are wound together and are        introduced into a bag of the metal plastic type. The gel        precursor is of the same nature as the precursor already        described in part 4b). The gel precursor is introduced in the        metal plastic bag after a complete vacuum. Polymerization is        obtained at 80° Celsius during 10 minutes or preferably with IR        (infra-red) once the battery has been sealed. A formation as in        the case of 4b is applied to the battery. The gel concentrations        in the separator and in the electrodes are different.        5. Other Technologies    -   The implementation of this new process is not limited to the use        of graphite as active material of the anode or to the use of        LiFePO₄ as active material of the cathode.    -   By way of example, a few anodes of the type Si, Li₄Ti₅O₁₂ or Sn        based alloys or the like may be mentioned; the cathode may        comprise LiCO₂ or LiMn_(0.5)Ni_(0.5)O₂, LiNi_(x)Co_(y)Al_(z) or        the like.    -   The gel may also be of the PVDF type or may consist of a mixture        of polyether+PVPF or polyether+PMMA or the like.    -   The process may easily be adapted for a hybrid super condenser        of the type:        -   5a) Li₄Ti₅O₂/electrolyte/carbon;        -   5b) WO₂/electrolyte/carbon;        -   5c) Graphite/electrolyte/carbon; and        -   5d) Si/electrolyte/carbon or other combination.

Example 1

Production of the anode is carried out by using a spherical graphitewhose particles have an average size of 20 μm. These particles have beenobtained by mechano-melting (Hosokawa, Japan). 95% of graphite is mixedwith 8% of STYRENE BUTADIENE RUBBER (STYRENE BUTADIENE RUBBER (SBR))dissolved in water. This mixture is applied on a copper collector by theDoctor Blade® method. The electrode thus obtained is dried under vacuumat 120° Celsius during 24 hours. This electrode is mounted opposite ametallic lithium and it is separated by a Celgard (EC-DMC-LIBF₄) type offilm. There is thus obtained an electrochemical cell with a 4 cm²surface.

The battery is cycled between 0.0 and 2.5 Volts at a rate of C/12. FIG.5 shows the result of the first two cycles of the cell with a coulombicefficiency of 82.0% and 96.1% respectively during the first and secondcycles.

Example 2

The cathode that is prepared contains particles of LiFePO₄ (PhostechInc.) coated with 3% Ketjen black. The coating process is carried out bymechano-melting (Hosokawa, Japan).

The compound LiFePO₄/carbon (Ketjen black) is mixed with 5% of STYRENEBUTADIENE RUBBER (STYRENE BUTADIENE RUBBER (SBR) dissolved in water.This mixture is applied on an aluminum collector by the Doctor Blade®method. The electrode thus obtained is dried under vacuum at 120°Celsius during 24 hours. This electrode is mounted opposite a metalliclithium and is separated by a Celgard type of film (EC-PC-DMC-LiBF₄).There is thus obtained an electrochemical cell with a 4 cm² surface.

The battery is cycled between 2.5 and 4.0 Volts at a rate of C/24. FIG.6 shows the electrochemical result of the first two cycles of the cellwith a coulombic efficiency of 90.0% and 99.7% respectively during thefirst and second cycle.

Although the present invention has been described by means of specificembodiments, it is understood that many variations and modifications maybe grafted to said embodiments, and the present invention aims atcovering such modifications, uses or adaptations of the presentinvention following in general, the principles of the invention andincluding any variation of the present invention that will become knownor are conventional in the field of activity of the present invention,and that may apply to the essential elements mentioned above, inaccordance with the scope of the following claims.

EMBODIMENTS

1. Process for preparing an electrode that is at least partly coatedwith a film obtained by spreading and drying, on an electrode support,an aqueous solution comprising at least one active material, at leastone water soluble binder and at least one water soluble thickener.2. Process according to embodiment 1, in which the active material isselected from the group consisting of:a. metallic oxides;b. ceramics;c. carbon, natural graphite and synthetic graphite;d. metals;e. semi-conductor materials; andf. mixtures of at least two thereof.3. Process according to embodiment 2, in which:a. the metallic oxide is selected from the group consisting of LiMn2O4,LiCoO2 and LiNiO2;b. the carbon is selected from the group consisting of high surface areacarbon, graphite, carbon fibers and cokes;c. the metals are selected from the group consisting of Ag, Sn, and Cu;andd. the semi-conductor material is Si.4. Process according to any one of embodiments 1 to 3, in which thechemically and/or electrochemically active material is in the form ofpowder whose average particle size is between 10 nanometers and 50micrometers.5. Process according to embodiment 4, in which the powder has a granulardispersion between 200 nanometers and 25 micrometers.6. Process according to any one of embodiments 1 to 5, in which at least20% of the binder and/or thickener are water soluble at the rate of 20grams in 100 grams of water, at room temperature.7. Process according to embodiment 6, in which at least 50% of thebinder and/or thickener are soluble.8. Process according to embodiment 7, in which at least 90% of thebinder and/or thickener are soluble.9. Process according to embodiment 8, in which the water solublethickener is selected from the group consisting of natural celluloses,modified celluloses, natural polysaccharides and modifiedpolysaccharides.10. Process according to embodiment 9, in which the soluble thickenerhas a molecular weight between 27,000 and 250,000.11. Process according to embodiment 9 or 10, in which the thickener isselected from the group consisting of carboxymethylcelluloses,hydroxymethylcelluloses and methylethylhydroxycelluloses.12. Process according to any one of embodiments 1 to 11, in which thethickener is selected from the group consisting ofcarboxymethylcelluloses of the type Cellogen®.13. Process according to embodiment 12, in which the thickener isselected from the group consisting of EP, 7A, WSC. BS-H and 3Hcarboxymethylcelluloses, sold by Daiichi Kogyo Seiyaku Co. of Japan.14. Process according to any one of embodiments 1 to 14, in which thebinder is a natural or synthetic rubber.15. Process according to any one of embodiments 1 to 14, in which thebinder is of the non-fluorinated type or of the low fluorinated type.16. Process according to embodiment 14 or 15, in which the rubber isselected from the group consisting of SBR's, NBR's, HNBR's, CHR's andACM's.17. Process according to embodiment 15 or 16, in which the rubber is aSBR characterized in the form of a paste at room temperature.18. Process according to embodiment 17, in which the STYRENE BUTADIENERUBBER (SBR) selected is the one sold by NIPPON ZEON'S BINDER BATTERYGRADE (BM-400B) or the like.19. Process according to any one of embodiments 13 to 18, in which thethickener is EP and/or 3H.20. Process according to any one of embodiments 1 to 19, in which theelectrode is an anode and the aqueous solution used for spreadingcontains by weight:a. at least 64% graphite; andb. at least 3% water soluble binder,c. from 0.1 to 2% thickener; andd. at most 27% water.21. Process according to any one of embodiments 1 to 19, in which theelectrode is a cathode and the aqueous solution used for spreadingcontains by weight:a. at least 64% LiFePO4; andb. at least 3% water soluble binder,c. from 0.1 to 2% thickener; andd. at most 27% water.22. Process according to any one of embodiments 1 to 21, in which atleast 95% of the water that is present in the spreading solution isevaporated after spreading.23. Process according to embodiment 22, in which the traces of H2O thatare present at the surface of the electrode, after its coating with theaqueous solution, are removed by heat treatment in line of the EXT, DBHand/or DB process or by Infrared, preferably at a temperature between 80and 130° Celsius for a period of time between 1 and 12 hours.24. Process according to embodiment 10, in which the electrode is of thenon-salted type.25. Process according to any one of embodiments 1 to 24, carried out inambient air and by using the Doctor Blade extrusion method and/or theelectrostatic method.26. Process according to any one of embodiments 1 to 20 and 22 to 25, inwhich the electrode is negative and the electrochemically activematerial used is selected from the group consisting of powders of thegraphite, alloy of Sn, of Si, Li4Ti5O12, WO2 types and mixtures of atleast two of these components.27. Process according to embodiment 26, in which the graphite powderconsists of ellipsoidal shaped particles coated with prismatic shapedgraphite particles.28. Process according to embodiment 20, in which coating of ellipsoidalgraphite with prismatic graphite is obtained by mechano-melting and/orby hybridization.29. Process according to any one of embodiments 1 to 19, 21 and 22 inwhich the electrode is positive and the electrochemically activematerial is selected from the group consisting of powders of LiCo2,LiNi2, Li2Mn2O4, LiNi0.5Mn0.5O2, LiFePO4 coated with graphite and carbonand mixtures of at least two thereof.30. Process according to embodiment 29, in which the electrode isprepared from particles of LiFePO4 coated with particles of graphiteand/or carbon.31. Process according to embodiment 30, in which the specific surfacearea of the carbon present in the coating, measured by BET, is ≥50 m2/g.32. Process according to embodiment 30 or 31, in which coating ofLiFePO4 with carbon and/or graphite is carried out by mechano-melting orby hybridization.33. Electrode consisting of a support coated at least in part with afilm containing one active material, said electrode being obtained byimplementation of one of the processes according to any one ofembodiments 1 to 25.34. Electrode according to embodiment 33, that is a cathode in which theelectrode support consists at least in part of stainless, aluminum,copper, carbon, metal-plastic or a mixture of at least two of thesematerials.35. Electrode according to embodiment 33 that is an anode in which theelectrode support consists at least in part of copper, metal-plastic, ora mixture of at least two thereof.36. Electrode according to any one of embodiments 33 to 35, having atleast one of the following properties:a. storage stability, preferably higher than 1 year, in the presence ofa moisture content higher than 50% and in the presence of temperatureshigher than 20° Celsius;b. a film thickness when the latter is graphite based that is between 10and 100 μm, still more preferably between 20 and 45 μm and according tothe most advantageous mode the film has a thickness of about 45 μm;c. a film thickness when the latter is iron and/or phosphate based thatis between 20 and 200 μm, still more preferably between 20 and 110 μm,the most advantageous mode being the one in which the film has athickness of about 90 μm;d. electrochemical performances that compare to those of correspondingelectrodes obtained with the same active material but by using anorganic solvent solution; ande. an electrode film characterized by the fact that particles of rubberare directly attached to the electrode support.37. Electrode according to embodiment 36, in which the porosity of thefilm that coats one or more of the electrodes, measured according to themethod of thickness measurement, is between 10 and 90%.38. Electrode according to embodiment 37, in which the porosity isbetween 30 and 40%.39. Process for preparing an electrochemical system from itsconstituents including at least one anode, at least one cathode and atleast one separator, in which at least one anode and/or at least onecathode has been obtained by a process described in any one ofembodiments 1 to 32 or as defined in any one of embodiments 33 to 38.40. Process according to embodiment 39 for the preparation of a batteryin which the separator is porous.41. Process for preparing an electrochemical battery according toembodiment 40, in which the separator is preferably of the PP or PE typeor of the (PP,PE) mixture type.42. Process according to any one of embodiments 39 to 41, in which theseparator is preferably obtained by extrusion.43. Process according to embodiment 39, in which the separator is of thegel type.44. Process according to embodiment 41, in which the separator isobtained from polymer materials of the type:

-   -   polyester,    -   poly(vinylydienefluoride) of chemical formula (CH2-CF2)n, with n        preferably varying between 1000 and 4000, preferably such that n        is close to 150, preferably those having an average molecular        weight between 10,000 and 1 million, still more preferably those        having an average molecular weight between 100,000 and 250,000;    -   poly(vinylydiene fluoro-co-hexafluoropropene) copolymers, of        formula [(CH2-CF2)x(CF2-CF(CF3))1-x]n in which n varies from        1000 to 4000, preferably n varies from 2000 to 3000, still more        preferably n is close to 150 and x preferably varies between        0.12 and 0.5, preferably those having an average molecular        weight between 10,000 and 1 million, still more preferably those        having an average molecular weight between 100,000 and 250,000;    -   poly(tetrafluoroethylenes), of chemical formula (CF2-CF2)n, with        n varying from 5 to 20,000, preferably n varying from 50 to        10,000, preferably those having an average molecular weight        between 500 and 5 million, still more preferably those having an        average molecular weight between 5,000 and 1,000,000, preferably        about 200,000;    -   poly(ethylene-co-propylene-co-5-methylene-2-norbornenes) or        ethylene propylene-diene copolymers, also called EPDM,        preferably those having an average molecular weight between        10,000 and 250,000, preferably between 20,000 and 100,000; and    -   the poly(methylmethacrylates) also called (PMMA), of formula        [(CH2-C(CH3)/(CO2CH3)]n, with n preferably varying between 100        and 10,000, still more preferably n varying from 500 to 5000,        preferably those having an average molecular weight between        10,000 and 1 million, preferably those having an average        molecular weight between 50,000 and 500,000; and    -   mixtures of at least two thereof.        45. Process according to embodiment 44, in which the separator        is of the polyether PEO-PPO copolymer type.        46. Process according to embodiment 44, in which the separator        is of the 3 branch polyether type or of the 4 branch polymer        type.        47. Process according to embodiment 46, in which the separator        is preferably of the 4 branch polymer type manufactured by DKS        Japan and sold under the trademark ELEXCEL® ERM1.        48. Electrochemical system that can be obtained by a process        comprising at least one process step as defined in any one of        embodiments 39 to 47.        49. Electrochemical system comprising at least one electrode        obtained by implementation of a process according to any one of        embodiments 1 to 32 or as defined in any one of embodiments 33        to 38, a separator of the gel, solid or liquid electrolyte type.        50. Electrochemical system according to embodiment 48 or 49,        comprising an electrolyte gel.        51. System according to embodiment 50 of the all liquid battery        type, in which the electrolyte includes at least one salt and at        least one solvent.        52. System according to embodiment 51, in which the salt molar        concentration, in the electrolyte, is lower than or equal to 1        and the solvent molar concentration is higher than or equal to        1.        53. System according to embodiment 51 or 52, in which the salt        is preferably a salt of the imide family, of the type LiPF6,        LiBF4, LiBOB, LiTFSI or LiFSI or a mixture of at least two of        the latter, such as mixtures of LiBOB and LiFSI.        54. System according to any one of embodiments 51 to 53, in        which the retained solvents have an elevated boiling point.        55. System according to embodiment 54, in which the solvent has        a boiling point higher than 100° Celsius.        56. System according to embodiment 55, in which the solvent is        of the type γBL, TESA, or modified TESA, or mixtures thereof.        57. System according to any one of embodiments 51 to 55, in        which EC and PC solvents are used for the formation of the        passivation film in the case of carbon based anodes, and PC        solvent for low temperature applications.        58. System according to embodiment 57, in which the electrolyte        for the all gel battery is obtained from a precursor made of a)        a polymer+b) a liquid electrolyte.        59. System according to embodiment 58, in which the a) content        varies from 1 to 99%, preferably this content varies from 5 to        25%; and the b) content varies from 1 to 99%, preferably, this        content varies from 75 to 95% and the a and b contents agree        with the relation (a)+(b)=100%, the % being given in weight.        60. System according to embodiment 59, in which a        thermo-initiator is added in amounts that are proportional to        the total weight a)+b), or preferably in amounts between 100 and        5000 ppm, preferably in amounts between 500 and 1000 ppm.        61. System according to embodiment 60, in which the composition        of the precursor is about 5% of a 4 branch polyether preferably        of the ELECEL type, and about 95% of an electrolyte of        composition (1.5 LiTFSI+EC+PC+TESA+γBL (1:1:1:2)).        62. System according to embodiment 61 in which, the        concentration in lithium salt is higher than or equal to 1 M (1        molar) for the gels.        63. System according to embodiment 61, in which, the        concentration in lithium salt is lower than or equal to 1 M (I        molar) in the liquid electrolyte.        64. Use of a water soluble polymer, preferably a polymer of the        Styrene Butadiene Rubber type, still more preferably a SBR sold        by NIPPON ZEON'S BINDER BATTERY GRADE (BM-400B) as binder in an        aqueous solution for the preparation of a film for coating part        or the totality of an electrode support.        65. Use according to embodiment 64, without any formation of HF.        66. Use according to embodiment 65, in which the formation of HF        is avoided by using an imide salt.        67. Use according to any one of embodiments 64 to 66, in which        the preparation of the film is carried out by cross-linking the        polymer solution that coats the electrode by using thermal        radiation after the electrode has been placed in the battery,        the battery is closed and sealed.        68. Use according to embodiment 67, in which cross-linking of        the polymer solution is preferably carried out by Infrared.        69. Use according to embodiment 67 or 68, in which the        polymerization temperature is between 40 and 80° Celsius.        70. Use according to any one of embodiments 64 to 69, in which        cross-linking of the polymer lasts between 5 minutes and 2        hours.        71. Use according to embodiment 70, in which the polymerization        is carried out at about 80° Celsius and during about 10 minutes.        72. Use according to any one of embodiments 64 to 71, in which        the battery is flexible and of the multilayer metal plastic        type.        73. Use according to embodiment 72, for reducing the weight and        cost of manufacture due to the fact that it is not required to        have a protective layer against HF, that is removed during the        process.        74. Use according to any one of embodiments 64 to 73, for the        preparation of super condensers preferably for the preparation        of hybrid type of super condensers.        75. Use according to any one of embodiments 64 to 73, in which        the cathode support is of the aluminum type preferably of the        EXMET® expanded metal type.        76. Use according to any one of embodiments 64 to 73, in which        the anode support is of the full copper type, preferably EXMET®        or conductive metal plastic when the average voltage is lower        than or equal to 1.6 Volts and the cathode support is of full        aluminum, preferably EXMET® or conductive metal plastic when the        average voltage is higher than 1.6 Volts.        77. Process for preparing an electrochemical separator at least        partly coated with a polymer type film, preferably of the SBR        type that is water soluble.        78. Process for preparing an electrochemical separator according        to the processes of preparing electrodes defined in any one of        embodiments 1 to 32, except that the aqueous polymer solution        that is used contains no active materials nor carbon, or very        small quantities thereof.        79. Electrochemical system including at least three constituents        namely at least one anode, at least one cathode and at least one        separator and in which at least two, and preferably at least        three of the constituents of the system have been prepared by        implementation of one of the processes according to any one of        embodiments 1 to 32 and/or by implementation of a process        according to embodiment 77 or 78.        80. Electrochemical system according to embodiment 79 in which        the constituents have been prepared without using organic        solvents.

The invention claimed is:
 1. A process for preparing an electrochemicalseparator comprising spreading an aqueous solution on a support, theaqueous solution comprising: at least one water soluble binder; and atleast one water soluble thickening agent, wherein the water solublethickening agent is selected form the group consisting of naturalcelluloses, modified celluloses, natural polysaccharides and modifiedpolysaccharides, wherein the aqueous solution is essentially free ofactive materials and carbon, and wherein the support comprises at leastone metal.
 2. The process according to claim 1, wherein constituents ofthe aqueous solution have been prepared without using organic solvents.3. The process according to claim 1, wherein the resultantelectrochemical separator has a porosity between 10 and 90%.
 4. Theprocess according to claim 1, wherein the resultant electrochemicalseparator has a porosity between 30 and 50%.
 5. The process according toclaim 1, wherein the aqueous solution is free of active materials andcarbon.
 6. The process according to claim 1, wherein at least 90% of thewater soluble binder and/or the water soluble thickening agent aresoluble at room temperature.
 7. The process according to claim 1,wherein the water soluble thickening agent has a molecular weightbetween 27,000 and 250,000.
 8. The process according to claim 1, whereinthe water soluble thickening agent is selected from the group consistingof carboxymethylcelluloses, hydroxymethylcelluloses andmethylethylhydroxycelluloses.
 9. The process according to claim 1,wherein the water soluble thickening agent is a carboxymethylcellulose.10. The process according to claim 1, wherein the water soluble binderis a natural or synthetic rubber.
 11. The process according to claim 1,wherein the water soluble binder is a water soluble rubber is selectedfrom the group consisting of SBRs, NBRs, HNBRs, CHRs and ACMs.
 12. Theprocess according to claim 1, wherein the water soluble binder is anSBR.
 13. The process according to claim 1, wherein the water solublebinder is an SBR in the form of a paste at room temperature.
 14. Theprocess according to claim 1, wherein the water soluble binder is anon-fluorinated binder.
 15. The process according to claim 1, whereinthe water soluble binder is a non-fluorinated SBR in the form of a pasteat room temperature.
 16. The process according to claim 1, wherein atleast 95% of the water that is present in the aqueous solution isevaporated after spreading.
 17. The process according to claim 16,further comprising heat treatment in line of an extrusion process or byinfrared.
 18. The process according to claim 17, wherein the heattreatment is conducted at a temperature between 80 and 130° Celsius fora period of time between 1 and 12 hours.
 19. The process according toclaim 1, wherein the spreading is carried out in ambient air and byusing an electrostatic method.
 20. An electrochemical separator preparedaccording to claim
 1. 21. The electrochemical separator according toclaim 20, wherein the separator is cross-linked by UV thermal heating,E-Beam, or IR.
 22. An electrochemical system comprising the separator ofclaim 20.